Process for the purification of hydrogen peroxide

ABSTRACT

Process for purification of aqueous solutions of hydrogen peroxide comprising the steps of adding one or more macroligands to said solution to form a mixture and forcing the mixture through an ultrafiltration membrane.

This application is a continuation of application Ser. No. 08/950,977,filed Oct. 15, 1997, now U.S. Pat. No. 5,851,402.

BACKGROUND OF THE INVENTION

(i) Field of the Invention

The present invention relates to a process for the purification ofaqueous solutions of hydrogen peroxide in order to remove cations andorganic acids therefrom.

(ii) Description of Related Art

Aqueous hydrogen peroxide has many industrial uses and, in the case ofthe electronics field, must exhibit a high purity and must therefore berid of its cations and organic acids.

The methods of purification described to date refer to distillation,treatment on ion exchange resins, as in French Patent Application FR 1043 082, treatment on exchange resins to which chelating agents areadded, in French Patent Application FR 2 624 500 and to a reverseosmosis process, as in U.S. Pat. No. 4,879,043.

However, these methods are not entirely satisfactory for the removal ofsome impurities such as especially the ferric Fe⁺⁺⁺ or aluminic Al⁺⁺⁺ions.

The present invention proposes to remedy these disadvantages.

SUMMARY OF THE INVENTION

The subject-matter of the invention is a process for the purification ofaqueous solutions of hydrogen peroxide, characterized in that one ormore macroligands are added to the solution and the resulting mixture isforced through an ultrafiltration membrane.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Aqueous solutions of aqueous hydrogen peroxide are usually employed inelectronics assays at from 30 to 35% by weight. The invention can,however, be applied to solutions assaying at up to 75% by weight.Macroligands are added to these aqueous solutions; the subject-matter ofthe invention is especially a process in which the macroligands containone or several functional groups chosen from carboxylic, sulphonic andphosphonic groups or nitrogen-containing functional groups such asaromatic or nonaromatic amine functional groups or N-oxidized aminefunctional groups.

Aqueous hydrogen peroxide to which the ligand(s) has (have) been addedis then forced under pressure through an ultrafiltration membrane. Themembrane is of an oxidation-resistant nature of the fluoropolymer type(PTFE, PVDF, PFA) and with a cut-off threshold adapted to the polymersemployed. The working pressure is from 1 bar to a few bars, in general 3to 4 bars; the subject-matter of the invention is particularly a processin which the ultrafiltration membrane is a membrane made offluoropolymer, especially of polyvinyl difluoride (PVDF), ofpolytetrafluoroethylene (PTFE) or of polyfluoroalkoxy (PFA).

The results of the tests developed in the examples mentioned below showthat results lower than 10 ppb (parts per billion) are obtained for theFe⁺⁺⁺ and Al⁺⁺⁺ ions when the macroligands are chosen from the4-vinylpyridine homopolymer, the styrene/4-vinyl-pyridine 2/8 and 1/9copolymers, acrylic phosphate/sulphonate copolymers (Mw=500 000),acrylic phosphate copolymer (Mw=500 000) and polyvinylphosphonic acid(Mw=30 000), this choice constituting a preferred alternative form ofthe present invention.

Besides the good results obtained, an advantage of this process consistsin it being possible for this method of purification to be used upstreamor downstream of other purification stages.

Another aspect of the invention is a process for the manufacture ofunstabilized ultrapure hydrogen peroxide from the crude product preparedaccording to the methods known to a person skilled in the art, such as,for example, the autooxidation of anthraquinone or of its derivatives,anodic oxidation of the SO₄ ⁻⁻ /HSO₄ ⁻ couple, cathodic reduction ofoxygen or the direct synthesis, optionally including one or morepurification stages chosen from distillation, passing over ion exchangeresins, passing over a column of adsorbents, especially of zeolites, orreverse osmosis, characterized in that it additionally includes at leastone ultrafiltration stage according to the process as defined above.

The ultrapure hydrogen peroxide thus produced corresponds to thestandards imposed by the users, especially the manufacturers ofelectronics components.

Another aspect of the present invention relates to a plant for theproduction of unstabilized ultrapure hydrogen peroxide, characterized inthat it includes

a) a hydrogen peroxide synthesis unit,

b) a unit for purification of the crude hydrogen peroxide obtained instage a), comprising at least one ultrafiltration stage according to theprocess, and

c) a storage vessel for the hydrogen peroxide purified in b), making itpossible to absorb the variation in the final user's consumption, andcharacterized in that the plant is situated on the same site as thefinal user of the purified hydrogen peroxide and especially on the siteof a factory for the manufacture of electronics components.

The following examples illustrate the invention without, however,limiting it.

EXAMPLE 1

A 70% strength aqueous hydrogen peroxide of industrial qualityoriginating from the anthraquinone process was diluted to 30% and hadadded to it 0.25% of acrylosulphonic copolymer of Mw=4500. This solutionwas then ultrafiltered on a Filtron® mini-ultrasette equipped with a 50cm² polyethersulphone membrane at a rate of 1 dm³ /min of retentate and1.3 cm³ /min of filtrate. Results (in ppb).

    ______________________________________                                        K           Fe     Al      Ni   Cr    Mn   Sn                                 ______________________________________                                        30% H.sub.2 O.sub.2                                                                   17      123    124   13   22    2    7800                             Filtrate                                                                              8       12     13    <4   5     <0.2 40                               ______________________________________                                    

EXAMPLE 2

0.25% by weight of polyvinylphosphonic acid of Mw=30 000 is added to a30% strength by weight aqueous hydrogen peroxide of electronics quality.The solution is then ultrafiltered on a Filtron 3K mini-ultrasette at arate of 1.5 dm³ /min of retentate and 0.7 cm³ /min of filtrate. Results(in ppb).

    ______________________________________                                                       K         Cu                                                   ______________________________________                                        30% H.sub.2 O.sub.2                                                                            0.95        0.94                                             Filtrate         0.45        0.21                                             ______________________________________                                    

EXAMPLE 3

0.25% by weight of 4-vinylpyridine homopolymer is added to industrialaqueous hydrogen peroxide. The resulting solution is ultrafiltered on 1Kmembrane. Results (in ppb)

    ______________________________________                                        Si           Fe      Al      Cr   P      Sn                                   ______________________________________                                        30% H.sub.2 O.sub.2                                                                   10 300   127     407   23   22 200 7700                               Filtrate                                                                              1680     3       <9    16   11 600 100                                ______________________________________                                    

EXAMPLE 4

Operating in a manner similar to Example 3, and employing asmacroligands a styrene/4-vinylpyridine 2/8 copolymer and the 1/9copolymer, following results are obtained:

    ______________________________________                                                Fe    Al       Cr      P       Sn                                     ______________________________________                                        30% H.sub.2 O.sub.2                                                                     70      140      17    23 800  7400                                 Filtrate  <4      <9       <4    11 200  <20                                  ______________________________________                                    

EXAMPLE 5

Operating as in Example 1, employing the macroligands cited below, thefollowing results are obtained:

    ______________________________________                                                    K     Fe      Al      Cr    Mg                                    ______________________________________                                        30% industrial H.sub.2 O.sub.2                                                              12      56      95    20    50                                  A             <8      16      40    <4    24                                  B             <8      8       <9    <4    14                                  C             <8      3       25    <4    30                                  D             <8      4       15    <4    2                                   ______________________________________                                    

A: acrylic/sulphonate copolymer

B: acrylic/phosphate/sulphonate copolymer Mw=500 000

C: acrylic/phosphate copolymer Mw=500 000

D: polyvinylphosphonic acid Mw=30 000.

What is claimed is:
 1. Process for purification of aqueous solutions ofhydrogen peroxide comprising the steps of adding one or moremacroligands to said solution to form a mixture and forcing the mixturethrough an ultrafiltration membrane, thereby producing a purifiedpermeate.
 2. Process according to claim 1, in which the macroligandscomprise at least one carboxylic, sulphonic, phosphonic ornitrogen-containing functional group.
 3. Process according to claim 2,in which the macroligand is 4-vinylpyridine homopolymer, astyrene/4-vinylpyridine 2/8 and 1/9 copolymer, anacrylic/phosphate/sulphonate copolymer (Mw=500 000), an acrylicphosphate copolymer (Mw=500 000) or polyvinylphosphonic acid (Mw=30000).
 4. Process according to claim 2, wherein said nitrogen-containingfunctional group is an aromatic, nonaromatic or N-oxidized aminefunctional group.
 5. Process according to claim 1, in which theultrafiltration membrane comprises a fluoropolymer.
 6. Process accordingto claim 5, wherein said fluoropolymer is PVDF, PTFE or PFA.
 7. Processaccording to claim 1, comprising synthesizing the hydrogen peroxide byautooxidation of anthraquinone or of its derivatives.
 8. Processaccording to claim 1 wherein said aqueous solution of hydrogen peroxideis obtained by autooxidation of anthraquinone or of its derivatives,anodic oxidation of an SO₄ ⁻⁻ /HSO₄ ⁻ couple, cathodic reduction ofoxygen or a direct synthesis.
 9. Process according to claim 8 furthercomprising the step, after obtaining the solution of hydrogen peroxidebut before mixing said hydrogen peroxide with said one or moremicroligands, of purifying said hydrogen peroxide by distillation,passing said solution over ion exchange resins, passing said solutionover a column of an adsorbent, or by reverse osmosis.
 10. Process formanufacturing unstabilized ultrapure hydrogen peroxide from a crudehydrogen peroxide comprising the steps of purifying the hydrogenperoxide by one or more purification stages selected from the groupconsisting, of reverse osmosis, distillation, ion exchange andadsorption; adding one or more microligands to said hydrogen peroxide toform a mixture; and forcing the mixture through an ultrafiltrationmembrane, thereby producing a purified permeate.